[MS63.1] Remove TrafficStats.TAG_SYSTEM_DOWNLOAD dependency

Replace with system Api.

Test: TH
Bug: 204830222
CTS-Coverage-Bug: 215043101
Change-Id: Ic14b26d2862f6fe8bee18fe0c9eaf183052452ee
diff --git a/core/api/system-current.txt b/core/api/system-current.txt
index 29957e4..3196ef9 100644
--- a/core/api/system-current.txt
+++ b/core/api/system-current.txt
@@ -7585,6 +7585,7 @@
   public class TrafficStats {
     method public static void setThreadStatsTagApp();
     method public static void setThreadStatsTagBackup();
+    method public static void setThreadStatsTagDownload();
     method public static void setThreadStatsTagRestore();
     field public static final int TAG_NETWORK_STACK_IMPERSONATION_RANGE_END = -113; // 0xffffff8f
     field public static final int TAG_NETWORK_STACK_IMPERSONATION_RANGE_START = -128; // 0xffffff80
diff --git a/packages/ConnectivityT/framework-t/src/android/net/TrafficStats.java b/packages/ConnectivityT/framework-t/src/android/net/TrafficStats.java
index 032bc3f..1af32bf 100644
--- a/packages/ConnectivityT/framework-t/src/android/net/TrafficStats.java
+++ b/packages/ConnectivityT/framework-t/src/android/net/TrafficStats.java
@@ -282,6 +282,18 @@
     }
 
     /**
+     * Set active tag to use when accounting {@link Socket} traffic originating
+     * from the current thread. The tag used internally is well-defined to
+     * distinguish all download provider traffic.
+     *
+     * @hide
+     */
+    @SystemApi
+    public static void setThreadStatsTagDownload() {
+        setThreadStatsTag(TAG_SYSTEM_DOWNLOAD);
+    }
+
+    /**
      * Get the active tag used when accounting {@link Socket} traffic originating
      * from the current thread. Only one active tag per thread is supported.
      * {@link #tagSocket(Socket)}.